Device for treating a packaging material by means of uv radiation

ABSTRACT

A device ( 1 ) for treating a packaging material ( 2 ) by means of UV radiation, the device having a source ( 6 ) of such radiation screen ( 8 ) interposed between the source ( 6 ) and the material ( 2 ) for treatment; the screen ( 8 ) has a film ( 9 ) of a polymer resistant and permeable to UV radiation, and which is flexible, does not tear, and does not form fragments.

TECHNICAL FIELD

The present invention relates to a device for treating a packagingmaterial by means of UV radiation.

UV radiation has long been used in a wide range of applications. In thefood industry, for example, it is commonly used for disinfecting orsterilizing packaging material, or for surface treating the foodproducts themselves.

UV radiation is also used for disinfecting work environments.

The device according to the present invention may conveniently be used,though not exclusively, in a packaging material sterilizing unit of apourable food product packaging machine, to which application referenceis made in the following description purely by way of a non-limitingexample.

BACKGROUND ART

Various types of machines are known for packaging various types ofpourable food products, such as fruit juice, wine, tomato sauce,pasteurized or long-storage (UHT) milk, etc.

Such machines have different characteristics, depending on the type ofpackage used, e.g. packages made of strip or sheet material, cups,bottles, tubs, etc.

One of the best-known packaging machines is the one marketed under theregistered trademark Tetra Brik®—referred to purely by way of anon-limiting example—in which the packages or packs are formed from acontinuous tube of packaging material defined by a longitudinally sealedweb.

The packaging material has a multilayer structure comprising a layer ofpaper material covered on both sides with layers of heat-seal material,e.g. polyethylene. In the case of aseptic packages for long-storageproducts, such as UHT milk, the packaging material comprises a layer ofbarrier material, e.g. aluminium foil, which is superimposed on a layerof heat-seal plastic material, and is in turn covered with another layerof heat-seal plastic material eventually defining the inner face of thepackage and therefore contacting the food product.

To produce aseptic packages, the web of packaging material is unwoundoff a reel and fed through a sterilizing unit, in which it issterilized, for example, by immersion in a bath of liquid sterilizingagent, such as a concentrated solution of hydrogen peroxide and water.

Alternatively, or in addition to being treated with a liquid sterilizingagent, the web of packaging material may be treated by exposure to oneor more sources of UV electromagnetic radiation, as described, forexample, in European Patent Application EP-A-919246.

Downstream from the sterilizing unit, the web of packaging material ismaintained in an aseptic chamber, in which it is dried, folded into acylinder, and sealed longitudinally to form a continuous vertical tube.In other words, the tube of packaging material forms an extension of theaseptic chamber, is filled continuously with the pourable food product,and is then fed to a forming and (transverse) sealing unit for producingthe individual packages, and in which the tube is gripped between pairsof jaws and sealed transversely to form aseptic pillow packs.

The pillow packs are separated by cutting the sealed portions inbetween, and are then fed to a final folding station where they arefolded mechanically into the finished form.

Packaging machines of the type described above are used widely andsatisfactorily in a wide range of food industries for producing asepticpackages from strip packaging material. Performance of the sterilizingunit, in particular, amply ensures conformance with regulationsgoverning the sterility of the packages.

Within the industry, however, a demand exists for further improvement,particularly as regards the safety of UV devices, which may be used forboth disinfecting and sterilizing various types of packaging material,such as strip and sheet material, cups, bottles, tubs, etc..

UV devices substantially comprise a UV radiation source housed in acasing and protected at the front by a screen made of material resistantand permeable to UV radiation. In commonly marketed devices, the screenis defined by a quartz plate.

Though perfectly suitable in terms of physical-chemical properties,quartz has various drawbacks. In particular, it is extremely expensive.Moreover, a quartz screen is fragile and, if broken, tends to formextremely hard, sharp fragments. In known machines, the UV device, andtherefore the quartz screen, is so located as to be protected againstimpact, so that the risk of it breaking and leaving trace fragments ofquartz on the packaging material is highly unlikely. Nevertheless, atpresent, the possibility cannot be entirely excluded. Though unlikely,breakage may be caused by anomalous vibration or thermal stress, byflaws in the structure of the material, by accidental forcing or impactduring assembly, or by a combination of any of these.

Another drawback of quartz in this type of application is its tendencyto dirty easily in normal operating conditions, and where it isextremely difficult, expensive, or even impossible to clean, whereasreplacement is far from cheap.

Quartz also has the further drawback of any flaws, cracks, dirt, etc.locally affecting its optical properties, thus possibly resulting inuneven irradiation of the material being treated.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a device for UVirradiation treatment of a packaging material, designed to eliminate theaforementioned hazards typically associated with known devices.

According to the present invention, there is provided a device fortreating a packaging material by means of UV radiation, the devicecomprising a source of said radiation, and a screen for protecting saidsource and which is interposed between the source and the material fortreatment; characterized in that said screen comprises a film of apolymer resistant and permeable to said UV radiation.

Using a film of a polymer resistant and permeable to UV radiationprovides for meeting the requirements of chemical/physical compatibilitywith the workplace, and at the same time for eliminating the drawbackstypically associated with quartz plates.

In particular, the flexibility of the polymer material substantiallyeliminates any risk of tearing caused by vibration or thermal stress.And, even in the highly unlikely event of the film tearing, no fragmentsare formed, thus making the material perfectly suitable for use in thefood industry.

Moreover, a film of polymer material is much cheaper than a quartzplate, and can therefore be replaced quickly and cheaply in the event ofsoiling.

Finally, in the event of flaws in the structure, i.e. on the surface, ofthe polymer film, uniform irradiation of the material being treated isunaffected, the polymer film being by nature slightly translucent andtherefore still capable of ensuring adequate UV radiation diffusion.

In a preferred embodiment of the present invention, the polymer isfluorinated or, better still, completely fluorinated and in theperfluoroalkoxy (PFA) class.

More preferably, the fluorinated polymer is an MFA, the characteristicsof which are particularly favourable in terms of UV radiationtransmission, even, for example, in the case of UV radiation with a 222nm wavelength, as described in the aforementioned European PatentApplication EP-A-919246.

In one possible embodiment of the invention, the polymer film issupported between substantially rigid grilles.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred, non-limiting embodiment of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows a section of a device for treating packaging material inaccordance with the invention;

FIG. 2 shows a partly exploded view in perspective of the FIG. 1 device.

BEST MODE FOR CARRYING OUT THE INVENTION

Number 1 in the accompanying drawings indicates as a whole a device fortreating a packaging material 2 for producing packages of a pourablefood product.

By way of a non-limiting example, the packaging material is a sheetmaterial.

Material 2 is fed continuously in known manner along a path P in a planea of the material.

Material 2 may be defined by a different type of material, such as atub, cup, bottle, etc.

Device 1 extends crosswise to material 2, i.e. perpendicularly to path Pand parallel to plane α, and comprises an elongated outer casing 3 openon the side facing material 2 so as to form a window 4 defined by aperipheral flange 5. Device 1 also comprises a UV radiation source 6housed longitudinally in casing 3, which is provided in conventionalmanner with a lining 7 of reflecting material.

Source 6 emits UV radiation of a wavelength, for example, of 222 nm.

The device also comprises a protective screen 8 fixed at the front toflange 5 so as to close window 4.

According to the present invention, screen 8 comprises a film 9 of apolymer material resistant and permeable to the UV radiation emitted bysource 6.

The polymer material may be of any type, providing it is transparent toUV radiation (T≧80%) and resistant to said UV radiation in the operatingconditions and for the time period between two successive replacements.

The polymer material may, for example, be in the polyolefin group, suchas PE or PP.

Depending on the different resistance to UV radiation of differentpossible types of polymer film, provision may be made for appropriate,programmed, periodic replacement of film 9 of polymer material, so as toensure constant mechanical and optical properties of the film.

Replacement may be made, for example, either at given times, orcontinuously, using a strip of polymer material moving continuouslybetween two appropriately powered reels.

In a preferred embodiment, the material is a fluorinated polymer, or acompletely fluorinated polymer in the perfluoroalkoxy (PFA) class, andeven more preferably is an MFA, e.g. the MFA produced by AUSIMONT® underthe trade name HYFLON® MFA.

Film 9 is conveniently 20 to 200 μm thick, is preferably 40 μm, 50 μm,or 100 μm thick, and is in the form of a flexible, slightly translucentfilm capable of diffuse transmission of a fraction of the incidentradiation.

Though film 9, by virtue of its physical characteristics, may be usedalone and simply fixed along the edges to flange 5, it is preferablyinterposed between two substantially rigid metal supporting grilles 10,which are fixed to flange 5 by means of respective peripheral frames 11,and provide for protecting and keeping the film flat.

Film 9 has excellent characteristics in terms of transmittance andresistance to ageing under UV radiation, as shown in the followingexamples.

EXAMPLE 1

A 50 μm thick film of Hyflon® MFA was exposed to 300 KJ/cm2 UV radiationof 222 nm wavelength for 800 hours. After exposure, the film showed novisible alteration, and 90% transmittance referred to the above 222 nmwavelength.

EXAMPLE 2

A 100 μm thick film of Hyflon® MFA was exposed to 300 KJ/cm2 UVradiation of 222 nm wavelength for 800 hours. After exposure, the filmshowed no visible alteration, and 82% transmittance referred to theabove 222 nm wavelength.

Film 9 does not tear in the event of anomalous thermal stress orvibration, and, even if torn by accidental impact, which issubstantially impossible in working conditions, does not producefragments.

Film 9 is also much cheaper than a conventional quartz plate.

Clearly, changes may be made to the present invention without, however,departing from scope of the invention itself.

In particular, the screen may be made of a different polymer material,e.g. PE, PP, PFA or many others.

Also, grilles 10 may be different or even dispensed with.

1. A device for treating a packaging material by means of UV radiation,the device comprising a source of said radiation, and a screen forprotecting said source and which is interposed between the source andthe material for treatment; wherein said screen comprises a film of apolymer resistant and permeable to said UV radiation.
 2. A device asclaimed in claim 1, wherein said polymer is fluorinated.
 3. A device asclaimed in claim 1, wherein said polymer is completely fluorinated.
 4. Adevice as claimed in claim 3, wherein said polymer is in theperfluoroalkoxy (PFA) class.
 5. A device as claimed in claim 4, whereinsaid polymer is an MFA.
 6. A device as claimed in claim 1, wherein saidfilm is of a thickness ranging between 20 and 200 μm.
 7. A device asclaimed in claim 6, wherein the thickness of said film is selectedbetween 40 μm or 100 μm.
 8. A device as claimed in claim 1, wherein saidscreen comprises a pair of substantially rigid grilles between whichsaid film is supported.